Whither Strange Pulsars ?

Both neutron stars and strange stars are capable of supporting fast rotations observed in pulsars. On the basis of this it has been argued that some of the pulsars could be strange stars. We investigate whether strange stars can sustain characteristic pulsar magnetic fields ($10^8 - 10^{13.5} Gauss$) over astronomically significant time-scales. Furthermore, we check whether strange stars fit into the general scenario of field evolution of pulsars. It is found that as far as the evolution of the magnetic field is concerned the strange pulsar hypothesis runs into serious difficulties to explain the observational data.Comment: 2 pages, no figure, LaTex, a shorter version, accepted for publication in `Bulletin of Astronomical Society of India

The Magnetar Fields

We discuss the nature of evolution of the magnetic field in Magnetars.Comment: 2 pages, LaTeX (basi.sty), poster presented in the annual meeting of ASI (2003

Gravity Defied (from potato asteroids to magnetised neutron stars) I : The self-gravitating objects

Gravitation, the universal attractive force, acts upon all matter (and radiation) relentlessly. Left to itself, gravity would pull everything together and the Universe would be nothing but a gigantic black hole. Nature throws almost every bit of physics - rotation, magnetic field, heat, quantum effects and so on, at gravity to escape such a fate. In this series of articles we shall explore systems where the eternal pull of gravity has been held off by one or another such means.Comment: First of a 4-article serie

Gravity Defied (from potato asteroids to magnetised neutron stars) IV. Neutron Stars (dead stars of the second kind)

A star burns its nuclear fuel and balances gravitation by the pressure of the heated gas, during its active lifetime. After the exhaustion of the nuclear fuel, a low mass star finds peace as a {\em white dwarf}, where the pressure support against gravitation is provided by Fermi-degenerate electrons. However, for massive stars the gravitational squeeze becomes so severe that in the final phase of evolution, the average density approximately equals the nuclear density. At such densities most of the protons combine with electrons to convert themselves into neutrons. A {\em Neutron star}, composed of such neutron-rich material, is host to some fascinating physics arising out of its amazingly compact state of matter (where a solar mass is packed inside a sphere of radius $\sim$ 10Km).Comment: Final instalment of a 4-article series (see arXiv:1703.09799, arXiv:1704.03770, arXiv:1705.04987

Evolution of the Magnetic Field in Accreting Neutron Stars

There has been sufficient observational indication suggesting a causal connection between the binary history of neutron stars and the evolution of their magnetic field. In particular, it is believed that the generation of the low-field millisecond pulsars is a consequence of the processing of normal high-field neutron stars in binary systems. We try to understand the mechanism of field evolution in neutron stars that are members of binary systems with an aim to understand the problem of millisecond pulsar generation. To this end we have looked at four related problems : i. the effect of diamagnetic screening on the final field of a neutron star accreting material from its binary companion; ii. evolution of magnetic flux located in the crust of an accreting neutron star; iii. application of the above-mentioned model to real systems and a comparison with observations; iv. an investigation into the consequences of magnetic flux being initially located in the core of the star and its observational implications.Comment: 6 pages, 4 postscript figures, Thesis presentation in 1999 meeting of Indian Astronomical Society, accepted for publication in 'Bulletin of Astronomical Society of India

Of Neutrinos and Magnetars

We discuss the nature of neutrino propagation in the presence of strong magnetic fields of Magnetars.Comment: 2 pages, LaTeX (basi.sty), poster presented in the annual meeting of ASI (2003

Magnetic Fields of Neutron Stars

This article briefly reviews our current understanding of the evolution of magnetic fields in neutron stars, which basically defines the evolutionary pathways between different observational classes of neutron stars. The emphasis here is on the evolution in binary systems and the newly emergent classes of millisecond pulsars.Comment: Has appeared in Journal of Astrophysics and Astronomy special issue on 'Physics of Neutron Stars and Related Objects', celebrating the 75th birth-year of G. Srinivasa

Magnetic Fields of Neutron Stars : The AMXP Connection

This article briefly reviews our current understanding (or lack thereof) of the evolution of magnetic fields in neutron stars, with an emphasis on the binary systems. In particular, the significance of the newly emerging population of accreting millisecond pulsars (AMXP) is discussed.Comment: v1 : 5 pages, 4 figure, uses basi.cls, submitted to ASI Conference Series on "Recent Trends in the Study of Compact Objects: Theory and Observation" | v2 : major modification of figures, minor changes in the tex

Gravity Defied (from potato asteroids to magnetised neutron stars) II : The failed stars

Gravitation, the universal attractive force, acts upon all matter (and radiation) relentlessly. Stable extended structures can exist only when gravity is held off by other forces of nature. This series of articles explores this interplay, looking at objects that just missed being stars in this particular instalment.Comment: Second of a 4-article series (see arXiv:1703.09799

Comments on "Strongly magnetized cold degenerate electron gas: Mass-radius relation of the magnetized white dwarf"

The super-massive white dwarf models proposed by Das & Mukhopadhyaya [Phys. Rev. D 86 042001 (2012)], based on modifying the equation of state by a super-strong magnetic field in the centre, are very far from equilibrium because of the neglect of Lorentz forces, as has recently been shown by Nityananda & Konar [arXiv:1306.1625].Comment: Comment on Das & Mukhopadhyay, Phys. Rev. D 86, 042001 (2012); brief summary of Nityananda & Konar, arXiv:1306.162